Instructions
Follow the instructions on your experiment cards to complete the four experiments listed below. As you work, use this sheet to record your predictions, observations, and conclusions. Think carefully about what you see happening at a microscopic level!
Part 1: Chemistry & Electricity
In these experiments, you will generate electricity using chemical reactions.
| Experiment | Prediction & Observation | Explanation |
|---|---|---|
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1(a) Lemon Battery You will use a lemon, a copper wire, and a magnesium strip to power an LED. |
Prediction: Will the LED light up? Why do you think so? Observations: Describe what happens when you connect the circuit. Do you see any changes on the surface of the magnesium or copper? |
What is the role of the lemon juice in this experiment? Where is the electrical energy coming from?
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1(b) Daniell Galvanic Cell You will use two different metal salt solutions, zinc, and copper to create a more powerful chemical battery. |
Prediction: Will this cell be able to power the LED? Do you think it will be stronger or weaker than the lemon battery? Observations: What happens to the surface of the zinc metal? What about the copper metal? |
Why do you need two different metals and two different solutions for this to work? What is the purpose of the fabric strip connecting them (the "salt bridge")?
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Part 2: The Slow Burn - Corrosion
In these experiments, you will investigate the process of rusting and how to prevent it.
| Experiment | Hypothesis & Observation | Conclusion |
|---|---|---|
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2(a) Rust Protection You will observe how an unprotected iron nail rusts and how a more reactive metal (magnesium) can protect it. |
Hypothesis: Which nail will rust more: the plain iron nail or the one connected to the magnesium strip? Why? Observations: Use the indicators provided. Describe the colours you see around the plain nail and the protected nail after some time. |
Explain how the magnesium strip protects the iron nail from rusting. This is called "sacrificial protection." Why is that a good name for it?
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2(b) Electricity vs. Iron You will use a battery to see how electricity can speed up or even reverse the corrosion process. |
Hypothesis: What do you think will happen to the iron nail connected to the positive terminal? What about the negative terminal? Observations: Describe the colours that appear around each of the two nails once the battery is connected. |
Which nail rusted (oxidised)? Which nail was protected? How does this relate to the flow of electrons from the battery?
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Think Like a Scientist
All four experiments involve metals, chemical reactions, and the movement of tiny particles called electrons. What is the one key difference between the "Chemistry & Electricity" experiments and the "Corrosion" experiments in terms of energy?
Answer Key
Part 1: Chemistry & Electricity
| Experiment | Prediction & Observation | Explanation |
|---|---|---|
| 1(a) Lemon Battery |
Prediction: Yes, the LED should light up because the two different metals in the acidic lemon juice will create a chemical reaction that produces electricity. Observations: The LED lights up. You may see tiny bubbles forming on the surface of the magnesium strip. The magnesium may start to look dull. |
The lemon juice is an acidic electrolyte. It allows charged particles (ions) to move between the metals. The electrical energy comes from a chemical reaction where the more reactive metal (magnesium) gives away its electrons, which then flow through the circuit to the less reactive metal (copper). This flow of electrons is electricity. |
| 1(b) Daniell Cell |
Prediction: Yes, it will power the LED. It should be stronger than the lemon battery because the metal salt solutions are more efficient electrolytes. Observations: The surface of the zinc metal will slowly dissolve or corrode. The copper metal will appear to get thicker or have a new layer of copper deposited on it. |
The two different metals have different tendencies to give up electrons. Zinc is more reactive and gives its electrons away (it oxidises). These electrons flow through the wire to the copper. In the copper sulphate solution, copper ions accept these electrons and turn into solid copper metal (it reduces), plating onto the copper strip. The salt bridge allows other ions to flow between the solutions to keep the charge balanced, which keeps the reaction going. |
Part 2: The Slow Burn - Corrosion
| Experiment | Hypothesis & Observation | Conclusion |
|---|---|---|
| 2(a) Rust Protection |
Hypothesis: The plain iron nail will rust more. The magnesium is more reactive than iron, so it will react instead of the iron. Observations: Around the plain nail, you see a dark blue colour (from the potassium hexacyanoferrate(III) indicator), showing that the iron is rusting. Around the nail connected to magnesium, you see a pink colour (from the phenol red indicator), showing a different reaction is happening, but no blue colour, so the iron is not rusting. |
Magnesium is more reactive than iron, meaning it gives up its electrons more easily. When connected to iron, the magnesium gives its electrons to the iron, which prevents the iron from reacting with oxygen and water to form rust. It is called "sacrificial protection" because the magnesium metal gets "sacrificed" (it corrodes) to save the iron. |
| 2(b) Electricity vs. Iron |
Hypothesis: The nail on the positive terminal will rust, and the nail on the negative terminal will be protected. Observations: A dark blue colour (rust indicator) appears around the nail connected to the positive terminal. A pink colour and bubbles appear around the nail connected to the negative terminal. |
The nail connected to the positive terminal rusted. The positive terminal pulls electrons away from the iron, causing it to oxidise (rust) very quickly. The nail connected to the negative terminal was protected. The negative terminal supplies a constant flow of electrons to the iron, preventing it from giving up its own electrons to oxygen, thus stopping rust from forming. |
Think Like a Scientist
The key difference is the direction of energy conversion. In the "Chemistry & Electricity" experiments, a spontaneous chemical reaction is used to produce electrical energy (chemical energy is converted to electrical energy). In the "Corrosion" experiments (specifically 2b), electrical energy from an outside source (a battery) is used to drive a chemical reaction (electrical energy is converted to chemical energy).
Teacher Rubric: Electrochemical Science (ACARA v9 Alignment)
This rubric assesses student understanding across the four experiments, with proficiency indicators aligned to Australian Curriculum (v9) Science achievement standards for Years 8-10.
| Criteria | Developing (Year 8 Level) | Achieving (Year 9 Level) | Excelling (Year 10 Level) |
|---|---|---|---|
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Scientific Investigation Skills (AC9S8I02, AC9S9I02, AC9S10I02) |
Follows procedure and makes simple observations about what can be seen (e.g., "the light turned on," "the nail changed colour"). | Makes detailed observations, accurately recording specific changes (e.g., "bubbles formed on the magnesium strip," "a blue colour appeared at the positive nail"). Forms a reasonable hypothesis based on prior knowledge. | Systematically records qualitative data and proposes explanations for observations during the experiment. Connects observations between different experiments to identify patterns. |
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Understanding: Energy Transformation (AC9S8U06) |
Identifies that chemical energy is being changed into electrical energy in the lemon battery and Daniell cell. States that the chemicals are the source of the power. | Explains that the flow of electricity is caused by a chemical reaction involving two different metals and an electrolyte. Can compare the effectiveness of the two cells. | Explains the process as a transfer of electrons from the more reactive metal (anode) to the less reactive metal (cathode), describing this as the basis for the energy transformation. |
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Understanding: Chemical Reactions (AC9S8U05, AC9S9U07, AC9S10U08) |
Describes rusting as a chemical change where iron turns into a new substance. Identifies that some things can stop rust. | Explains corrosion as a chemical reaction involving iron, water, and oxygen. Describes sacrificial protection and electrolysis as useful applications of chemistry to control reactions. | Explains corrosion and its prevention in terms of oxidation and reduction (redox). Identifies the nail at the positive terminal as the site of oxidation (loss of electrons) and the nail at the negative terminal as the site of reduction (gain of electrons). |
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Analysis & Synthesis (AC9S8I06, AC9S9I06, AC9S10I06) |
States that both sets of experiments use metals and chemicals. | Draws a conclusion that chemical reactions can either produce electricity (galvanic cells) or be driven by electricity (electrolysis). | Synthesises concepts from all four experiments to explain that the direction of spontaneous electron flow (based on metal reactivity) determines whether a system is a galvanic cell or an electrolytic cell. |